Polymer-modified asphalt with wax additive

ABSTRACT

An improved method forms and employs a wax to modify asphalt. The method includes: (a) selecting a solid polymeric material, (b) heating the solid polymeric material in an extruder to produce a molten polymeric material, (c) filtering the molten polymeric material, (d) placing the molten polymeric material through a chemical depolymerization process in a reactor to produce a depolymerized polymeric material, and (e) adding the depolymerized material to a pre-wax mixture to produce a polymer-modified asphalt. The addition of wax reduced the mixing time necessary to achieve improved polymer dispersion compared to the control formulation modified bitumen and reduced the viscosity of the neat bitumen. Pre-polymer addition of wax is detrimental to most properties of the resulting modified asphalt. Post-polymer addition improved viscosity reduction, higher softening point and improved dimensional stability.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority benefit fromInternational Application No. PCT/CA2017/050172 filed on Feb. 13, 2017,entitled “Polymer-Modified Asphalt With Wax Additive” which, in turn,claims priority benefit from U.S. Application Ser. No. 62/295,035 filedon Feb. 13, 2016, also entitled “Polymer-Modified Asphalt With WaxAdditive”. The '172 and '035 applications are hereby incorporated byreference herein in their entireties.

FIELD OF THE INVENTION

The present invention relates to a method of creating synthetic waxesfrom recycled plastic material, and employing the waxes as additives inasphalt processing and modification.

BACKGROUND OF THE INVENTION

Additives in asphalt processing and modifications are commonplace.However, use of wax to improve the physical properties andprocessability of roofing asphalt, also known as flux, has not beenemployed to any significant extent.

In the recent past, there have been considerable efforts to convertpolymeric solid wastes into useful products. Existing conversionprocesses are not efficient and can release green-house gases into theenvironment.

A low cost method of producing wax that can be employed to achieveimproved processing and more desirable physical characteristics ofpolymer modified asphalt, while ensuring good blending of the asphaltand polymer additive, would be commercially advantageous. Such a methodwould ideally employ a readily available, inexpensive feedstock,preferably recyclable material, and employ an economical process.

SUMMARY OF THE INVENTION

Shortcomings of conventional methods of producing additive-modifiedasphalt are overcome by a method for forming a wax and employing the waxto modify asphalt. The process comprises:

-   -   (a) selecting a solid polymeric material;    -   (b) heating the solid polymeric material in an extruder to        produce a molten polymeric material;    -   (c) filtering the molten polymeric material;    -   (d) placing the molten polymeric material through a chemical        depolymerization process in a reactor to produce a depolymerized        wax material;    -   (e) adding the depolymerized wax material to a pre-wax mixture        to produce a polymer-modified asphalt.

The present method can be continuous or semi-continuous.

In the present method, the polymeric material can be one or more ofhigh-density polyethylene, low density polyethylene, linear low-densitypolyethylene, and polypropylene. The polymeric material can containrecycled plastics.

In a preferred method, the polymeric material and the pre-wax asphaltblend contain recycled plastics.

The present method can further comprise:

-   -   (f) filtering the solid polymeric material.

The present method can further comprise:

-   -   (f) cooling the depolymerized polymeric material.

The present method can still further comprise:

-   -   (g) purifying the depolymerized polymeric material.

The purifying step can employ one of flash separation, absorbent beds,clay polishing and film evaporators.

In the present method, the depolymerized material is preferably added tothe pre-wax asphalt blend mixture via an in-line pump. The pre-waxmixture can comprise the solid polymeric material and atacticpolypropylene.

The present method can further comprise:

-   -   (f) employing gas and oil produced during purification of the        depolymerized polymeric material as fuel for at least one step        of the method.

The filtering can employ one of a screen changer and a filter bed.

In a preferred method, the depolymerization process preferably employs acatalyst. The preferred catalyst employs a zeolite or alumina support.

In a preferred method, the depolymerization process employs a secondreactor. The reactors can be connected in series and can be stackedvertically. One or more of the reactors can include a static mixer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart illustrating a process for creating a wax andemploying it as an additive in asphalt modification.

FIG. 2 is a schematic diagram of a system for producing wax from plasticfeedstocks.

FIG. 3 is a cross-sectional side elevation view of a catalytic reactorwith a removable static mixer configured to be heated via thermalfluid/molten salt.

FIG. 4 is a cross-sectional front elevation view of a group of catalyticreactors of the type shown in FIG. 3, arranged in parallel.

FIG. 5 is a cross-section side elevation view of the parallel catalyticreactor arrangement of FIG. 4, shown in a horizontal configuration.

FIG. 6 is a cross-section side elevation view of a vertical helicalinternal catalytic reactor arrangement with two reactors connected inseries.

FIG. 7 is a perspective view of a horizontal reactor with an internalhelical mixer.

FIG. 8 is a table of micrographs showing polymer fluorescence underultraviolet (UV) light exposure for Control Formulation, Wax BlendFormulation 1, and Wax Blend Formulation 2.

FIG. 9 is a set of photographs showing linear dimensional changes of 25cm by 25 cm samples stored for 24 hrs at 80° C. for Control Formulation,Wax Blend Formulation 1, and Wax Blend Formulation 2.

FIG. 10 is a set of photographs of weathering panels for ControlFormulation, Wax Blend Formulation 1, and Wax Blend Formulation 2.

FIG. 11 is a table of micrographs showing polymer fluorescence underultraviolet (UV) light exposure for Control Formulation, Wax BlendFormulation 3 (pre-polymer addition), and Wax Blend Formulation 3(post-polymer addition).

FIG. 12 is a set of photographs showing linear dimensional changes of 25cm by 25 cm samples stored for 24 hrs at 80° C. for Control Formulation,Wax Blend Formulation 3 (pre-polymer addition), and Wax BlendFormulation 3 (post-polymer addition).

FIG. 13 is a pair of photographs showing linear dimensional changes of25 cm by 25 cm samples stored for 24 hrs at 80° C. for Wax BlendFormulation 3 (pre-polymer addition) and Wax Blend Formulation 3(post-polymer addition).

FIG. 14 is a set of photographs of weathering panels for ControlFormulation, Wax Blend Formulation 3 (pre-polymer addition) and WaxBlend Formulation 3 (post-polymer addition).

FIG. 15 is a pair of photographs showing the results of a Stain Indextest (ASTM D2746) for Wax Blend Formulation 3 (pre-polymer addition) andWax Blend Formulation 3 (post-polymer addition).

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENT(S)

A process of converting polymeric material, such as waste polymericmaterial, into wax is described below. The wax can then be employed tomodify asphalt. Waxes are compatible with a wide variety of asphaltadditives, and can be combined with a variety of materials commonlyemployed to improve the quality of asphalts.

In some embodiments, the addition of the wax improves the processing andphysical characteristics of the polymer modified asphalt, including:

-   -   reduction in blend time to achieve optimal or near-optimal        dispersion of the polymer, resulting in higher throughputs;    -   enablement of higher recycled asphalt (RAP) and recycled asphalt        shingle (RAS) loading through reduced mix stiffness and        increased lubricity; and    -   compaction and material handling.

In other or the same embodiments, the addition of wax improves thephysical characteristics of the final asphalt product. The resultingfinal products can have various properties that differ from theirunmodified forms. In some embodiments, the properties include, amongother things, improved force ductility; increased softening point;thermal stability; improved polymer dispersion and viscosity.Improvements to elastomeric properties and energy of deformation arealso observed in some embodiments.

The present method involves two main concepts: (1) the creation of thesynthetic wax via depolymerization of plastics, and then (2) adding thiswax to polymer modified asphalt. In some embodiments, the plastic stockemployed to produce the synthetic wax is the same stock employed toproduce the polymer modified asphalt.

FIG. 1 illustrates process 600 for creating synthetic waxes and thenusing those waxes to produce polymer modified asphalt. Process 600 canbe run in batches, but more preferably is a continuous process. Theparameters of Process 600, including but not limited to temperature,flow rate of plastic and total number of pre-heat, reaction, or coolingsegments, can be modified to produce end products of varying molecularweights and structural properties. For example raising the temperatureand/or decreasing the flow rate through Wax Creation Stage 2000 willresult in waxes of a lower molecular weight. Wax Creation Stage 2000allows for precise targeting of specific wax characteristics, such asthose that maximize the desire effect of blending.

In Material Selection Stage 1, polymeric feed is selected and/orprepared for treatment. In some embodiments, the polymeric feed insorted/selected to include polyethylene material. The polymer can beHDPE, LDPE, LLDPE, or other variations of polyethylene.

In other embodiments, the polymeric feed in sorted/selected to includepolypropylene material. In other embodiments, the polymeric feed insorted/selected to include both polyethylene and polypropylene material.In some embodiments, the feed can contain up to 20% polypropylene, lowerlevels of polystyrene, PET, EVA, PVC, EVOH, and undesirable additivesand/or contaminants, such as fillers, dyes, metals, various organic andinorganic additives, moisture, food waste, dirt, or other contaminatingparticles.

In some embodiments, the material selected in Material Selection Stage 1comprises recycled plastics. In other or the same embodiments, thematerial selected in Material Selection Stage 1 comprises recycledplastics and/or virgin plastics.

The polymeric feed for Material Selection Stage 1 can come from eitherPlastic Feed A1 or Plastic Feed A2. When the feed comes from PlasticFeed A2, the resulting wax will have a similar composition when it isadded with more plastic from Plastic Feed A2 to produce Finished AsphaltE. This leads to a more homogenous product with improved hightemperature thermal and structural properties.

In some embodiments, the material selected in Material Selection Stage 1is heated in an extruder and undergoes Pre-Filtration Process 3. In someembodiments the extruder is employed to increase the temperature and/orpressure of the incoming plastic and is employed to control the flowrates of the plastic. In some embodiments, the extruder is complimentedby or replaced entirely by pump/heater exchanger combination.

Pre-Filtration Process 3 can utilize both screen changers and filterbeds, along with other filtering techniques/devices to removecontaminants from and purify the heated material. The resulting filteredmaterial is then moved into an optional Pre-Heat Stage 4 which bringsthe filtered material to a higher temperature before it entersDepolymerization Stage 5. Pre-Heat Stage 4 can employ, among otherdevices and techniques, static and/or dynamic mixers and heat exchangerssuch as internal fins and heat pipes.

Material in Depolymerization Stage 5 undergoes depolymerization. Thisdepolymerization can be a purely thermal reaction or it can employcatalysts. Depending on the starting material and the desired endproduct, depolymerization could be employed for a slight or extremereduction of the molecular weight of the starting material.

In some embodiments, the catalyst employed is a zeolite or aluminasupported system or a combination of the two. In some embodiments, thezeolite contains aluminum oxide. In some embodiments, the catalyst isprepared by binding a ferrous-copper complex to an alumina or zeolitesupport and reacting it with an inorganic acid.

Depolymerization Stage 5 can employ a variety of techniques/devicesincluding, among other things, horizontal and/or vertical reactors fixedbed or batch reactors, and/or static mixers. In some embodiments,Reaction Stage 5 employs multiple reactors and/or reactors divided intomultiple sections to produce a semi-continuous or continuous process.

After Depolymerization Stage 5, the depolymerized material either entersCooling Stage 6 or is pumped via In-line Pump 8 and mixed with Pre-WaxMixture H during Wax Adding Stage 9 to produce Finished Asphalt E.

Cooling Stage 6 can employ heat exchangers, along with othertechniques/devices to bring the depolymerized material down to aworkable temperature before it enters optional Purification Stage 7 oris pumped via In-line Pump 8 and mixed with Pre-Wax Mixture H during WaxAdding Stage 9 to produce Finished Asphalt E.

In some embodiments, cleaning/purification of the material via suchmethods such as nitrogen stripping occurs before Cooling Stage 6.

Purification Stage 7 involves the refinement and/or decontamination ofthe depolymerized material. Techniques/devices that can be employed inPurification Stage 7 include, but are not limited to, flash separation,absorbent beds, clay polishing, distillation, vacuum distillation andfiltration to remove solvents, oils, color bodies, ash, inorganics, andcoke. In some embodiments a thin or wiped film evaporator is employed toremove gas, oil, and/or grease from the depolymerized material. In someembodiments the oil, gas and grease can in turn be burned to help runvarious Stages of Process 10.

In some embodiments a wiped film evaporator is used to remove gas, oil,and/or grease from the depolymerized material. In some embodiments, theoil, gas and grease can in turn be burned to help run various Stages ofProcess 2000. In some embodiments, the purified material is pumped viaIn-line Pump 8 and mixed with Pre-Wax Mixture H during Wax Adding Stage9 to produce Finished Asphalt E. In other embodiments, the purifiedmaterial is processed as a solid Finished Wax C that can then beemployed as Wax Feed F in Asphalt Modification Stage 3000.

Wax Creation Stage 2000 ends at Wax C in which the initial startingmaterial selected in Material Selection Stage 1 has been turned into WaxC. In at least some embodiments, Wax C is included as part of Wax FeedF. In some embodiments, Wax C is not highly branched and instead has amore linear structure.

Asphalt Modification Stage 3000 involves combining plastic from PlasticFeed A2 with a synthetic wax. In some embodiments, Plastic Feed A2,Filler Feed B and Polymer Feed G, which preferably comprises atacticpolypropylene (APP) and/or styrene-butadiene-styrene (SBS), are mixedtogether to form Pre-Wax Mixture H. A synthetic wax is then added,either via In-line Pump 8 or Wax Feed F in Wax Adding Stage 9 beforeFinished Asphalt E is produced. In some embodiments, the synthetic waxcan be added to Pre-Wax Mixture H; however tests have found improvedproperties when the wax is added afterwards.

When the synthetic wax is added via In-line Pump 8, some steps in theprocess can be eliminated, such as cooling the wax (Cooling Stage 6),purifying the wax (Purification Stage 7) and/or transporting the waxfrom one location to another.

In some embodiments, the wax in Wax Feed F was produced via Wax CreationStage 2000.

In some embodiments, the percentage of wax in the wax/asphalt compoundis roughly 0.1 to 25 percent by weight. The above method can employ avariety of waxes, including those with melt points between 60-160°Celsius, and viscosities 5-3000 cps, preferable in the range 110-130°C., and 100-2000 cps.

Changes in melting point and viscosity of the wax can change theproperties of the asphalt mixture.

Referring to FIG. 2, System 1000 includes reactor 700 with five reactormodules 102(a) through 102(e). Reactor modules 102 can vary indimensions and/or be connected in parallel and/or series. In otherembodiments, various numbers of reactor modules 102 can be employed. Theability to customize the number of reactor modules 102 allows forgreater control of the amount of depolymerization. System 1000 is oftenused in Wax Creation Stage 2000.

System 1000 can include hopper 111 for receiving polymeric materialand/or directing the supply of the polymeric material to optionalextruder 106. In some embodiments, extruder 106 processes the polymericmaterial received from hopper 111 by generating a molten polymericmaterial. The temperature of the polymeric material being processed byextruder 106 is controlled by modulating the level of shear and/or theheat being applied to the polymeric material by extruder heater(s) 105.Extruder heaters can use a variety of heat sources including, but notlimited to, electric, thermal fluids, and/or combustion gases. The heatis modulated by a controller, in response to temperatures sensed bytemperature sensor(s) 107.

In some embodiments, pressure sensor 109 measures the pressure of themolten polymeric material being discharged from extruder 106, toprevent, or at least reduce, risk of pressure spikes. The dischargedmolten polymeric material is pressurized by pump 110 to facilitate itsflow through heating zone 108 and reactor 100. While flowing throughreactor 100, the reactor-disposed molten polymeric material contacts acatalyst material which causes depolymerization.

Pressure sensor(s) 109 and/or temperature sensor(s) 107 can also beemployed to measure temperature and/or pressure, respectively, of thereactor-disposed molten polymeric material as it flows through reactor100. Pressure sensor(s) 109 can monitor for plugs before and/or aftereach reaction zones. Pressure sensor(s) 109 can also maintain systempressure below a maximum pressure such as the maximum pressure ofreactor 700 is designed for. Over-pressure can be controlled by feedbackfrom pressure transmitter 109 to a controller which transmits a commandsignal to shut down extruder 106 and pump 110, and thereby prevent thepressure from further increasing.

In cases when shutdown of extruder 106 does not relieve the overpressure, dump valve 117 can be opened into a container to removematerial from system 1000 and avoid an over pressure situation. Duringshutdown dump valve 117 can be opened to purge system 1000 with nitrogento remove leftover material to avoid clogs and degraded material duringthe next start up.

System 1000 can also include a pressure relief device, such as a reliefvalve or a rupture disk, disposed at the outlet of extruder 106, torelieve pressure from system 1000, in case of over-pressure.

Temperature sensor(s) 107 can facilitate control of the temperature ofthe reactor-disposed molten polymeric material being flowed throughreactor 100. This allows more precise control of the chemical reactionand the resulting polymerization. Temperature sensor(s) 107 also aid inmaintaining the temperature below a predetermined maximum temperature,for example the maximum design temperature of reactor 100.

The temperature is controlled by a controller (not shown), whichmodulates the heat being applied by heaters 118 disposed in heattransfer communication with the reaction zones 102(a) through 102(e) ofreactor 100, in response to the temperatures sensed by temperaturesensor(s) 119.

System 1000 can also include a pressure relief device, such as a reliefvalve or a rupture disk, disposed at the outlet of extruder 106, torelieve pressure from system 10, in case of over-pressure.

Flow control can also be provided for within system 1000. In someembodiments, system 1000 includes valve 115, disposed at the dischargeof extruder 106, for controlling flow from extruder 106 to other unitoperations within system 1000. Valve 116 facilitates recirculation.Valve 117 enables collection of product.

During operation, valve 115 can be closed in order to recirculate themolten polymeric material and increase the temperature of the moltenpolymeric material to a desired temperature. In this case valve 116would be open, valve 117 would be closed, extruder 106 would be “OFF”,and pump 110 would be recirculating.

Generated molten product material 112 is cooled within heat exchanger114, which can be, among other ways, water jacketed, air cooled, and/orcooled by a refrigerant. A fraction of the cooled generated moltenproduct material can be recirculated (in which case valve 116 would beopen), for reprocessing and/or for energy conservation.

In some embodiments, system 1000 is configured for purging by nitrogento mitigate oxidation of the molten product.

In System 1000 reactor 700 includes one or more reactor modules. Eachreactor modules includes a respective module reaction zone in which thereactor-disposed molten polymeric material is brought into contact witha catalyst material over a module-defined residence time, therebycausing depolymerization of the flowing reactor-disposed moltenpolymeric material. In some of these embodiments, the module-definedresidence time of at least two of the reactor modules is the same orsubstantially the same. In some of these embodiments, as between atleast some of the plurality of module-defined residence times aredifferent. In some embodiments, the catalyst material of at least two ofthe reactor modules is the same or substantially the same. In otherembodiments, the catalyst material of at least two of the reactormodules is different.

In some embodiments, each of the reactor modules includes areactor-disposed molten polymeric material-permeable container thatcontains the catalyst material. The container is configured to receivemolten polymeric material such that at least partial depolymerization ofat least a fraction of the received molten polymeric material iseffected by the catalyst material, and to discharge a molten productmaterial that includes depolymerization reaction products (and can alsoinclude unreacted molten polymeric material and intermediate reactionproducts, or both). Flowing of the reactor-disposed molten polymericmaterial through the reactor-disposed molten polymericmaterial-permeable container effects contacting between the catalystmaterial and the reactor-disposed molten polymeric material, foreffecting the at least partial depolymerization of at least a fractionof the reactor-disposed molten polymeric material. In this respect, theflowing reactor-disposed molten polymeric material permeates through thecatalyst material within the container, and while permeating through thecatalyst material, contacts the catalyst material contained within thecontainer, for effecting the at least partial depolymerization of atleast a fraction of the reactor-disposed molten polymeric material.

In System 1000 a first reactor is assembled from the reactor modules.The first reactor has a first reaction zone and includes a total numberof “P” reactor modules from “N” reactor modules, wherein “N” is a wholenumber that is greater than or equal to one.

Each one of the “N” reactor modules defines a respective module reactionzone including a catalyst material disposed therein, and is configuredfor conducting a flow of reactor-disposed molten polymeric materialthrough the respective module reaction zone, such that, flowing of thereactor-disposed molten polymeric material through the respective modulereaction zone brings it into contract with the catalyst material,thereby causing at least partial depolymerization of at least a fractionof the flowing reactor-disposed molten polymeric material. In thisrespect, the first reaction zone includes “P” module reaction zones.

When “N” is a whole number that is greater than or equal to two, eachone of the “N” reactor modules is configured for connection, in series,to one or more of the other “N” reactor modules such that a plurality ofreactor modules are connected to one another, in series, and includes aplurality of module reaction zones that are disposed in fluidcommunication within one another, in series, such that the total numberof module reaction zones correspond to the total number of connectedreactor modules. The plurality of connected reactor modules isconfigured for conducting a flow of reactor-disposed molten polymericmaterial through the plurality of module reaction zones, such that itcomes into contact with the catalyst material, thereby effecting atleast partial depolymerization of at least a fraction of the flowingreactor-disposed molten polymeric material.

When “P” is a whole number that is greater than or equal to two, theassembling of the first reactor includes connecting the “P” reactormodules to one another, in series, such that “P” reaction zones aredisposed in fluid communication with one another in series.

In the embodiment illustrated in FIG. 2, “P” is equal to five, such thatreactor 700 includes five reactor modules 102(a) through 102(e), thereaction zone consisting of five module reaction zones 104(a) through104(e), each one respective to a one of the five reactor modules. “P”can be more or less than five.

Molten polymeric material, for supplying to the constructed reactor, isgenerated by heating a polymeric material. In some embodiments, theheating is caused by a heater. In FIG. 2 the heating is produced by acombination of extruder 106 and separate heater 108. In suchembodiments, the generated molten polymeric material is forced from theextruder, flowed through a separate heater, and then supplied to themodule reaction zone. In some embodiments, the extruders are configuredto supply sufficient heat to the polymeric material such that thegenerated molten polymeric material is at a sufficiently hightemperature for supply to the reactor, and a separate heater is notrequired.

In FIG. 2, pump 110 receives molten polymeric material from extruder 106and effects transport (or flowing) of the molten polymeric materialthrough heater 108, and then through the first reaction zone. In someembodiments, extruder 106 is configured to impart sufficient force toeffect the desired flow of the generated molten polymeric material, suchthat pump 110 is optional.

In some embodiments, the molten polymeric material is derived from apolymeric material feed that is heated to effected generation of themolten polymeric material. In some embodiments, the polymeric materialfeed includes primary virgin granules of polyethylene. The virgingranules can include low density polyethylene (LDPE), linear low densitypolyethylene (LLDPE), high density polyethylene (HDPE), polypropylene(PP), or a mixture including combinations of LDPE, LLDPE, HDPE, and PP.

In some embodiments, the polymeric material feed includes wastepolymeric material feed. Suitable waste polymeric material feeds includemixed polyethylene waste, mixed polypropylene waste, and a mixtureincluding mixed polyethylene waste and mixed polypropylene waste. Themixed polyethylene waste can include low density polyethylene (LDPE),linear low density polyethylene (LLDPE), high density polyethylene(HDPE), polypropylene (PP), or a mixture including combinations of LDPE,LLDPE, HDPE and PP. In some embodiments, the mixed polyethylene wastecan include film bags, milk jugs or pouches, totes, pails, caps,agricultural film, and packaging material. In some embodiments, thewaste polymeric material feed includes up to 10 weight % of materialthat is other than polymeric material, based on the total weight of thewaste polymeric material feed.

The molten polymeric material is supplied to the reactor, and the moltenpolymeric material is flowed through the first reaction zone (i.e.including the “P” reaction zones) as reactor-disposed molten polymericmaterial. The flowing of the reactor-disposed molten polymeric materialthrough the first reaction zone brings it into contact with the catalystmaterial generating a molten product material, including adepolymerization product material (and, in some embodiments, alsoincludes unreacted molten polymeric material and/or intermediatereaction products). The molten product material is then collected.

In some embodiments, the catalyst is prepared by binding aferrous-copper complex to an alumina support and reacting it with aninorganic acid to obtain the catalyst material. Other suitable catalystmaterials include zeolite, mesoporous silica, alumina and H-mordenite.The system can also be run in the absence of a catalyst and producewaxes through thermal degradation.

The generated molten product material is discharged from andcollected/recovered from the reactor. In some embodiments, thecollection of the molten product material is effected by discharging aflow of the molten product material from the reactor. In thoseembodiments, with a plurality of reactor modules, the molten productmaterial is discharged from the first reactor module and supplied to thenext reactor module in the series for effecting further depolymerizationwithin the next reactor module in the series, and this continuesas-between each adjacent pair of reactor modules in the series.

In some embodiments, the generated depolymerization product materialincludes waxes, greases, oils, fuels, and C1-C4 gases, and grease-basestocks. Commercially available greases are generally made by mixinggrease base stocks with small amounts of specific additives to providethem with desired physical properties. Generally, greases include fourtypes: (a) a mixture of mineral oils and solid lubricants; (b) blends ofresiduum (residual material that remains after the distillation ofpetroleum hydrocarbons), uncombined fats, rosin oils, and pitches; (c)soap thickened mineral oils; and (d) synthetic greases, such aspoly-alpha olefins and silicones.

In some embodiments, the polymeric feed material is one of, or acombination of, virgin polyethylene (any one of, or combinations of,HDPE, LDPE, LLDPE and medium-density polyethylene (MDPE)), virginpolypropylene, or post-consumer, or post-industrial, polyethylene orpolypropylene (exemplary sources including bags, jugs, bottles, pails,and/or other items containing PE or PP), and it is desirable to convertsuch polymeric feed material into a higher melting point wax (having amelting point from 106° C. to 135° C.), a medium melting point wax(having melting point from 86° C. to 105° C.), and a lower melting pointwax (having a melting point from 65° C. to 85° C.), an even lowermelting point wax (having a melting point from 40° C. to 65° C.), usingan embodiment of the system disclosed herein.

In each case, the conversion is effected by heating the polymeric feedmaterial so as to generate molten polymeric material, and thencontacting the molten polymeric material with the catalyst materialwithin a reaction zone disposed at a temperature of between 325° C. and450° C. The quality of wax (higher, medium, or lower melting point wax)that is generated depends on the residence time of the molten polymericmaterial within the reaction zone. When operating in a continuous systemdepending on the flowrate of the extruder or gear pump residence timesvary from 1-120 minutes, preferably 5-60 minutes, with 1-12 reactormodules attached in series. In some of these embodiments, the supply andheating of the polymeric feed material is effected by a combination ofan extruder and a pump, wherein the material discharged from theextruder is supplied to the pump. In some of these embodiments, extruder106 is a 10 HP, 1.5 inch (3.81 cm) Cincinnati Milacron PedestalExtruder, Model Apex 1.5, and the pump 110 is sized at 1.5 HP for a 1.5inch (3.81 cm) line.

A pressure transducer PT01 monitors for plugs within the extruder (aswell as prior to PT02, see below) for maintaining system pressure belowa maximum pressure (namely, the maximum design pressure of the reactor100). Likewise, pressure transducer PT02 monitors for plugs elsewherewithin the system. Over-pressure is controlled by feedback from thepressure transmitted by PT01 and PT02 to a controller which transmits acommand signal to shut down the extruder 106 and the pump 110, andthereby prevent the pressure from further increasing.

In some embodiments, reactor 100 is first reactor 100, and the reactionzone of the first reactor is a first reaction zone, and the flowing ofthe molten polymeric material, through the first reaction zone, issuspended (such as, for example, discontinued).

When “P” is equal to one, the modifying includes connecting a totalnumber of “R” of the “N−1” reactor modules, which have not been used inthe assembly of the first reactor, to the first reactor, in which “R” isa whole number from 1 to “N−1”, such that another reactor is added andincludes a total number of “R+1” reactor modules that are connected toone another, in series, and such that the another reactor includes asecond reaction zone including “R+1” module reaction zones. Then anotherreactor is configured to conduct a flow of molten polymeric material,such that flowing of the reactor-disposed molten polymeric materialthrough the second reaction zone effects generation of anotherdepolymerization product material and its discharge from the anotherreactor.

When “P” is a whole number that is greater than or equal to two, butless than or equal to “N−1”, the modifying includes either one of:

-   -   (a) removing a total number of “Q” of the “P” reactor modules        from the first reactor, wherein “Q” is a whole number from one        to “P−1”, such that another reactor is added and includes a        total number of “P-Q” reactor modules that are connected to one        another, in series, and such that the another reactor includes a        second reaction zone including “P-Q” module reaction zones,        wherein the another reactor is configured to conduct a flow of        molten polymeric material, such that flowing of the        reactor-disposed molten polymeric material through the second        reaction zone effects of generation of another depolymerization        product material and its discharge from the another reactor, or    -   (b) connecting a total number of “R” of the “N−P” reactor        modules, which have not been employed in the assembly of the        first reactor, to the first reactor, wherein “R” is a whole        number from 1 to “N−P”, such that another reactor is added and        includes a total number of “P+R” reactor modules that are        connected to one another, in series, and also includes a second        reaction zone including “P+R” module reaction zones, wherein the        another reactor is configured to conduct a flow of molten        polymeric material, such that flowing of the reactor-disposed        molten polymeric material through the second reaction zone        effects generation of another depolymerization product material        and its discharge from the another reactor;

When “P” is equal to “N”, the modifying includes removing a total numberof “Q” of the “P” reactor modules from the first reactor, wherein “Q” isa whole number from one to “P−1”, such that another reactor is added andincludes a total number of “P−Q” reactor modules that are connected toone another, in series, and such that the another reactor includes asecond reaction zone, including “P−Q” module reaction zones. The anotherreactor is configured to conduct a flow of molten polymeric material,such that flowing of the reactor-disposed molten polymeric materialthrough the second reaction zone effects generation of anotherdepolymerization product material and its discharge from the anotherreactor.

In some embodiments, after the modifying of the first reactor to effectcreation of another reactor (by either one of connecting/adding orremoving reactor modules), another reactor is employed to generate asecond depolymerization product material. In this respect, polymericmaterial is heated to generate a molten polymeric material, and themolten polymeric material is flowed through the second reaction zone, toeffect generation of a second depolymerization product material. Thesecond depolymerization product material is then collected from thereactor.

In some embodiments, the same catalyst material is disposed within eachone of the “N” reactor modules.

In some embodiments, the reaction zone of each one of the “N” reactormodules is the same or substantially the same.

FIG. 3 shows a cross-section side-elevation view of catalytic reactor700 with removable static mixer 710 configured to be heated via thermalfluid and/or molten salt. Static mixer 710 provides greater mixing incatalytic reactor 700 and can result in the need of a lower operatingtemperature. In other embodiments, catalytic reactor 700 can include anannular insert. In other embodiments, catalytic reactor 700 can haveempty internals. In certain embodiments, catalytic reactor 700 employselectric heating.

The tubular configuration of catalytic reactor 700 offers severaladvantages in addition to those already mentioned above. In particular,use of tubular reactors connected in series allows for dependable andconsistent parameters, which allows for a consistent product.Specifically, a consistent flow through the tubular sections produces amore predictable and narrow range of end products than would be producedusing a continuous stirred reactor, as the surface area of the catalystand heat input is maximized. One advantage over continuous stirredreactors is elimination of shortcutting, flow in tubular sectionhypothetically moves as a plug. Each hypothetical plug spends the sameamount of time in the reactor. Tubular catalytic reactors can beoperated vertically, horizontally, or at any angle in between. Tubularcatalytic reactors (the reactor sections) and the corresponding pre-heatsections and cooling sections can be a universal size or one of severalstandard sizes. This allows not only for a consistent flow of thematerial, but also allows for tubular elements to be designed to beinterchangeable among the various section and easily added, removed,cleaned, and repaired. In at least some embodiments, the inner face ofthe tubular sections are made of 304 or 316 steel.

The thermal fluid and/or molten salt can enter jacket 720 viainlet/outlets 730. In some embodiments, catalytic reactor 700 a isconfigured to be mounted with a thermocouple/pressure transducer (notshown) and includes relevant notches 735. Notches 735 are used to bringthe thermocouple/pressure transducer in physical contact with the fluid.In some embodiments the thermocouple/pressure transducer will be mountedin a well, which reduces the material in-between the fluid and thesensor.

In some embodiments, catalytic reactor 700 includes removable screen 760that can hold the catalyst. Removable screen 760 can be easily replacedovercoming disadvantages associated with packed bed reactors, includingthermal gradients and challenging maintenance requirements and resultingdowntime. In some embodiments, the standardization of removable screen760 results in a consistent product leaving each section and/or allowsfor standardization across multiple reactors.

In other or the same embodiments, catalytic reactor 700 a can includeremovable adaptor 740 with cut-outs for static mixer supports. Staticmixer supports reduce the force on static mixers 710 allowing for moreforceful/rapid removal. The cut-outs of adaptor 740 improve the sealbetween the adapter and the screens. Catalytic reactor 700 a can includeflanges 750 on one or both ends to connect catalytic reactor 700 a toother reactors, extruders or the like.

FIG. 4 is a cross-section front-elevation view of a group of catalyticreactors 700 like the one shown in FIG. 3 arranged in parallel. Parallelarrangements allow for the total rate of production to be more readilyincrease/decreased as desired with minimal changes to the overallarrangement and allow multiple different levels of depolymerization tooccur at once.

Housing 800 allows catalytic reactors 700 to be bathed in thermaloil-molten salt which is often more effective than electric. The thermaloil-molten salt is contained in chamber 780. In some embodiments, flange770 allows for multiple housings to be joined together.

FIG. 5 is a cross-section side-elevation view of the parallel catalyticreactor arrangement of FIG. 25 show in a horizontal configuration.Parallel arrangement allows for higher flowrate units to be built withsmaller pressure drops that could cause issues as compared to a singletube arrangement. Horizontal configurations are often more convenient tooperate/maintain. The parallel catalytic reactor arrangement can also beoriented in a vertical configuration.

FIG. 6 is a cross-section side-elevation view of vertical helicalinternal catalytic reactor arrangement 900 with two reactors 700 likethe one shown in FIG. 3 connected in series. Horizontal helical mixerpre-heat section 820 is connected to one reactor 700. Helical mixers canlead to better mixing by avoiding stagnancies and hot spots.

Helical mixer cooling segment 830 is shown connected to the otherreactor 700 at a 45° decline. The decline allows for the product to flowvia gravity, while the 45 degree angle allows for sufficient contactbetween the cooling medium and the product.

In the embodiments shown, vertical helical internal catalytic reactorarrangement 900 has several inlet/outlets to allow for the use ofthermal fluid/molten salt mixtures however other warming techniques(such as, but not limited to, electric heating) can be employed as well.In other embodiments, annular catalytic reactor and/or reactors withempty internal volumes can be employed. In the same or otherembodiments, electric heating can employed to heat reactor 700.

FIG. 7 is a perspective view of horizontal reactor configuration 910with internal helical reactor 700 configured to employ electric heaters870 like the one shown in FIG. 3. In FIG. 7 the reactor shell has beenremoved from part of horizontal reactor configuration 910 to aid invisualizing the location of internal helical reactor 700.

Specific Examples of Plastics Modified by Synthetic Waxes

In an illustrative embodiment of the present process, wax was producedfrom the depolymerization of post-consumer polyethylene. 3% by weight ofthe wax (melting point 115° C.) was mixed with an asphalt composition,the softening point increased from 217° C. (with no wax) to 243° C., thepenetration decreased from 15 dmm to 11 dmm.

In another embodiment of the present process, 2% of wax, melting point115° C. is added to polymer modified bitumen. The addition of waxreduces mixing time from 10.5 hours to 8 hours and the viscosity ofasphalt mixture is reduced. Softening point of the mixture is increased,penetration is reduced and elastomeric properties are improved.Dimensional stability at 80° C. is improved, with 5 times reduceddeflection in the transverse, 3 times reduced deflection in parallel.Force ductility at 25° C. is improved by 100%.

In another embodiment of the present process, 4% of wax, melting point125° C. is added to polymer modified bitumen. The addition of waxreduces mixing time from 10.5 hours to 7 hours. Softening point of themixture is increased, penetration is reduced and elastomeric propertiesare improved. Dimensional stability is improved, with 5 times reduceddeflection in the transverse, 5 times reduced deflection in parallel.Force ductility is improved by 100%. Mixing can be achieved by anymethod common in asphalt processing.

Specific Examples of Plastics Modified by Synthetic Waxes

In an illustrative embodiment of the present process is for the additionof 3% of wax, melting point 115° C., resulting from the depolymerizationof post-consumer polyethylene. When mixed with an asphalt composition,the softening point increased from 217° C. (with no wax) to 243° C., thepenetration decreased from 15 dmm to 11 dmm.

In another embodiment of the present process, 2% of wax, melting point115° C. is added to polymer modified bitumen. The addition of waxreduces mixing time from 10.5 hours to 8 hours and the viscosity ofasphalt mixture is reduced. Softening point of the mixture is increased,penetration is reduced and elastomeric properties are improved.Dimensional stability at 80° C. is improved, with 5 times reduceddeflection in the transverse, 3 times reduced deflection in parallel.Force ductility at 25° C. is improved by 100%.

In another embodiment of the present process, 4% of wax, melting point125° C. is added to polymer modified bitumen. The addition of waxreduces mixing time from 10.5 hours to 7 hours. Softening point of themixture is increased, penetration is reduced and elastomeric propertiesare improved. Dimensional stability is improved, with 5 times reduceddeflection in the transverse, 5 times reduced deflection in parallel.Force ductility is improved by 100%.

In the mixing of the present polyethylene waxes, the melting pointranging from 45° C. to 135° C., viscosity ranging from 3 to 4000centipoise (cP) at 140° C. with asphalt. Mixing can be achieved by anymethod common in asphalt processing.

Effect of Two Different Waxes on Selected Properties of a ModifiedBitumen Compound Used for Commercial Roofing

As set forth in Table 2 below, Control Formulation consisted of 90% byweight of Base Asphalt (PRI Stock: Mid Continent) and 10% by weight ofSBS (Kraton D1101).

Wax Blend Formulation 1 consisted of 86% by weight of Base Asphalt (PRIStock: Mid Continent), 10% by weight of SBS (Kraton D1101) and 4% byweight of Wax 1 (melting point 115° C.; produced by depolymerization ofpost-consumer polyethylene).

Wax Blend Formulation 2 consisted of 86% by weight of Base Asphalt (PRIStock: Mid Continent), 10% by weight of SBS (Kraton D1101) and 4% byweight of Wax 2 (melting point 125° C.; produced by depolymerization ofpost-consumer polyethylene).

TABLE 1 Sample Data Ingredient Grade/Type Source Asphalt 150/200Penetration PRI Stock: Mid SBS SBS Linear Kraton D1101 LimestoneLimestone Filler Tamko (Shingle) Wax Wax 1 Applicant Wax 2

The preparation of the three blends for testing in this example(unfilled and filled with limestone) was as follows:

-   -   (1) The asphalt was heated to 180° C.    -   (2) 10% by weight SBS was added to the asphalt while high        sheared mixing condition was maintained for 30 minutes, followed        by 4% wax addition when applicable, then low shear agitation was        established for the remaining of the mixing until full        dispersion was achieved.    -   (3) During the maturation phase, aliquot samples were taken for        microscopy fluorescence analysis.    -   (4) For the filled samples, 20% by weight of limestone was added        while low shear agitation was maintained during 1 h at 180° C.

TABLE 2 Summary of Blends and Mix Times Control Wax Blend Wax BlendIngredient Source Formulation Formulation 1 Formulation 2 Base Asphalt,wt % PRI Stock: Mid 90 86 86 Continent SBS, wt % Kraton D1101 10 10 10Wax, wt % Wax 1 0 0 4 Wax 2 0 4 0 Property Results: Mix Time, ControlWax Blend Wax Blend hrs Specification Formulation Formulation 1Formulation 2 Fluorescence 2 Achieve phase undispersed undispersedundispersed Microscopy 3 inversion and undispersed undispersedundispersed 4 therefore full undispersed undispersed undispersed 5dispersion undispersed undispersed undispersed 6 undispersed undispersedundispersed 7 undispersed fully dispersed Fully dispersed 8 undispersed— — 9 undispersed — — 10 undispersed — — 10.5 fully dispersed — —

TABLE 3 Filled Modified Bitumen Properties Results: Control Wax BlendWax Blend Formulation Formulation 1 Formulation 2 CTMB (FailTemperature), ° C. D5147M −23.9 −23.9 −23.9 Softening Point, ° C. D3693.6 105.8 102.2 Penetration, dmm  4° C. D5 41 34 35 25° C. 50 40 39 46°C. 90 60 55 Elastic Recovery, %  4° C. D6084 B 76.2 56.3 63.8 10° C.90.0 90.0 86.25 25° C. 95.0 95.0 90.0 Heat Stability Transverse D5147/+10 +1.2 +2 (dimensional Direction D1204 stability)*, Parallel +6.4 +1.6+1.2 % Change direction Force Force ratio 25° C. T 300M 0.37 0.54 0.52Ductility (f1/f2) Deformation 3.2 5.4 6.0 Energy, (J/cm2)

FIG. 8 is a table of micrographs showing polymer fluorescence underultraviolet (UV) light exposure for Control Formulation, Wax BlendFormulation 1, and Wax Blend Formulation 2. For highly modified asphalt,a phase inversion occurs and the asphalt (black areas) becomes thedispersed phase within the polymer phase. The compatibility is deemedsatisfactory when a homogenous dispersion of the asphalt within thepolymer matrix is achieved.

FIG. 9 is a set of photographs showing linear dimensional changes of 25cm by 25 cm samples stored for 24 hrs at 80° C. for Control Formulation,Wax Blend Formulation 1, and Wax Blend Formulation 2, in accordance withASTM D1204.

FIG. 10 is a set of photographs of weathering panels for ControlFormulation, Wax Blend Formulation 1, and Wax Blend Formulation 2. Thepanels were monitored for visual changes to include wax exudation aswell as dimensional changes and weight loss due to UV and/or thermaldegradation of the polymer.

The following conclusions can be drawn from the foregoing test results:

-   -   The addition of both Wax 1 and Wax 2 reduces the mixing time        necessary to achieve the optimum polymer dispersion (phase        inversion) compared to the control Modified Bitumen (MB).    -   The addition of Wax Blend Formulations 1 and 2 increases the        softening point and viscosity of the MB while reducing the        penetration at 25° C. The increase in viscosity and reduction in        penetration is typically not desirable and might be mitigated by        a wax and SBS content adjustment.    -   The low temperature flexibility assessed by the Cold Temperature        Mandrel Bending test was not affected by the addition of Wax        Blend Formulations 1 and 2.    -   Both waxes significantly improved the heat stability at 80° C.        of the MB compared to the control MB.    -   The elastomeric properties were reduced for Wax Blend        Formulations 2 at 4° C., 10° C. and 20° C., but were maintained        for Wax Blend Formulation 1 at 10° C. and 20° C. but reduced at        4° C.    -   The energy of deformation at 25° C. was significantly improved        by the addition of both Wax Blend Formulations 1 and 2, as        compared to the control MB.    -   The addition of both Wax Blend Formulations 1 and 2 reduced the        storage stability of the filled MB compound.

Effect of Processing Conditions on the Characteristics and Performancesof the Polymer Modified Bitumen (PMB) formulated with 2% of Wax 2

As set forth in Table 5 below, Control Formulation consisted of 90% byweight of Base Asphalt (PRI Stock: Mid Continent) and 10% by weight ofSBS (Kraton D1101).

Wax Blend Formulation 3 (pre-polymer addition) consisted of 98% byweight of Base Asphalt (PRI Stock: Mid Continent), 0% by weight of SBS(Kraton D1101) and 2% by weight of Wax 2 (melting point 125° C.;produced by depolymerization of post-consumer polyethylene).

Wax Blend Formulation 3 (post-polymer addition) consisted of 88% byweight of Base Asphalt (PRI Stock: Mid Continent), 10% by weight of SBS(Kraton D1101) and 2% by weight of Wax 2 (melting point 125° C.;produced by depolymerization of post-consumer polyethylene).

TABLE 4 Sample Data Ingredient Grade/Type Source Asphalt 150/200Penetration PRI Stock: Mid Continent SBS SBS Linear Kraton D1101Limestone Limestone Filler Tamko (Shingle Filler) Wax Wax 1 Applicant

The preparation of the Wax Blend Formulation 3 for testing in thisexample (unfilled and filled with limestone) was as follows:

-   -   (1) The asphalt was heated to 180° C.    -   (2) 2% of the wax blend formulation was added under agitation        for 1 hour.    -   (3) 10% SBS was added to the asphalt while high sheared mixing        condition was maintained for 30 minutes, then low shear        agitation was established for the remaining of the mixing.    -   (4) During the maturation phase, aliquot samples were taken for        microscopy fluorescence analysis.    -   (5) For the filled samples, 20% of limestone was added while low        shear agitation was maintained during 1 h at 180° C.    -   (6) For Wax Blend Formulation 4, the wax was added 30 minutes        after the polymer addition, in a manner similar the preparation        of Wax Blend Formulations 1 and 2 previously discussed.

TABLE 5 Summary of Blends and Mix Times Wax Blend Wax Blend Formulation3 Formulation 3 Neat (pre-polymer (post-polymer Control IngredientSource Bitumen addition) addition) Formulation Base Asphalt, wt %Phillips 66 100 98 88 90 SBS, wt % Kraton D1101 0 0 10 10 Wax, wt %Applicant 0 2 2 0 Results: Wax Blend Wax Blend Property Formulation 3Formulation 3 Mix Time, Neat (pre-polymer (post-polymer Control hrsSpecification Bitumen addition) addition) Formulation Fluorescence 2Achieve phase — undispersed undispersed undispersed Microscopy 3inversion — undispersed undispersed undispersed 4 and — undispersedundispersed undispersed 5 therefore full — undispersed undispersedundispersed 6 dispersion — undispersed undispersed undispersed 7 —undispersed undispersed undispersed 8 — fully dispersed fully dispersedundispersed 9 — fully dispersed fully dispersed undispersed 10.5 — fullydispersed fully dispersed fully dispersed

TABLE 6 Polymer Modified Bitumen Properties Results: Wax Blend Wax BlendFormulation 3 Formulation 3 Test (pre-polymer (post-polymer Wax BlendControl Property Method addition) addition) Formulation 2 Formulation 1CTMB (Failure Temperature), ° C. D5147M −10.0 −21.1 −23.9 −23.9Softening Point, ° C. D36 104.2 101.4 105.8 93.6 Penetration, dmm  4° C.D5 34 41 34 41 25° C. 43 53 40 50 46° C. 99 134 60 90 Elastic Recovery,%  4° C. D6084 B 85.8 77.5 56.3 76.2 10° C. 87.5 83.3 90.0 90 25° C.97.5 96.8 95.0 95 Heat Stability Transverse 80° C. D5147/D1204 +0.4 +2.0+1.2 +10 (dimensional Direction stability), % Parallel +0.8 +2.0 +1.6+6.4 Change direction Force Force ratio 25° C. T 300M 0.29 0.18 0.540.37 Ductility (f1/f2) Deformation 4.51 3.14 5.4 3.2 Energy, (J/cm2)

FIG. 11 is a table of micrographs showing polymer fluorescence underultraviolet (UV) light exposure for Control Formulation, Wax BlendFormulation 3 (pre-polymer addition), and Wax Blend Formulation 3(post-polymer addition. For highly modified asphalt, a phase inversionoccurs and the asphalt (black areas) becomes the dispersed phase withinthe polymer phase. The compatibility is deemed satisfactory when ahomogenous dispersion of the asphalt within the polymer matrix isachieved.

FIG. 12 is a set of photographs showing linear dimensional changes of 25cm by 25 cm samples stored for 24 hrs at 80° C. for Control Formulation,Wax Blend Formulation 3 (pre-polymer addition), and Wax BlendFormulation 3, in accordance with ASTM D1204. The polymer added to WaxBlend Formulation 3 was poly(styrene-butadiene-styrene) (SBS).

FIG. 13 is a pair of photographs showing linear dimensional changes of25 cm by 25 cm samples stored for 24 hrs at 80° C. for Wax BlendFormulation 3 (pre-polymer addition) and Wax Blend Formulation 3(post-polymer addition). The polymer added to Wax Blend Formulation 3was SBS.

FIG. 16 is a set of photographs of weathering panels for ControlFormulation, Wax Blend Formulation 3 (pre-polymer addition) and WaxBlend Formulation 3 (post-polymer addition). The panels were monitoredfor visual changes to include wax exudation as well as dimensionalchanges and weight loss due to UV and/or thermal degradation of thepolymer.

FIG. 15 is a pair of photographs showing the results of a Stain Indextest (ASTM D2746) for Wax Blend Formulation 3 (pre-polymer addition) andWax Blend Formulation 3 (post-polymer addition). The Stain Index testmeasures the tendency for oil components to separate spontaneously fromasphalt. The separation of oil components can cause staining in asphaltroofing products and adjacent materials in storage and use. The resultsshow no staining in comparison to the control, which is expected due tothe wax improving thermal stability of the asphalt.

The following conclusions can be drawn from the foregoing test results:

-   -   (1) The addition of Wax 2 in Wax Blend Formulation 3:        -   (a) reduced the mixing time necessary to achieve the optimum            polymer dispersion (phase inversion) compared to Control            Formulation Modified Bitumen (MB) previously tested.        -   (b) reduced slightly the viscosity of the neat bitumen.    -   (2) The order of addition of the wax had a significant impact on        the product characteristics and performances:        -   (a) The pre-polymer addition process was detrimental to all            properties except for the softening point, the elastomeric            and cohesion properties and the dimensional stability.        -   (b) The post-polymer addition process improved a series of            properties over the control blend:            -   (i) Viscosity reduction            -   (ii) Higher softening point            -   (iii) Improved dimensional stability.    -   (3) No noticeable stain formation was detected for both of Wax        Blend Formulation 3 (pre-polymer addition) and Wax Blend        Formulation 3 (post-polymer addition).

While particular elements, embodiments and applications of the presentinvention have been shown and described, it will be understood, that theinvention is not limited thereto since modifications can be made withoutdeparting from the scope of the present disclosure, particularly inlight of the foregoing teachings.

What is claimed is:
 1. A method for forming a wax and employing said waxto modify asphalt, the method comprising: (a) selecting a solidpolymeric material; (b) heating said solid polymeric material in anextruder to produce a molten polymeric material; (c) filtering saidmolten polymeric material; (d) placing said molten polymeric materialthrough a chemical depolymerization process in a reactor to produce adepolymerized wax material; (e) adding said depolymerized wax materialto a pre-wax mixture to produce a polymer-modified asphalt.
 2. Themethod of claim 1, wherein said method is continuous or semi-continuous.3. The method of claim 1, wherein said polymeric material is one or moreof high-density polyethylene, low density polyethylene, linearlow-density polyethylene and polypropylene.
 4. The method of claim 1,wherein said polymeric material contains recycled plastics.
 5. Themethod of claim 1, wherein said polymeric material and said pre-waxmixture contain recycled plastics.
 6. The method of claim 1, furthercomprising: (f) filtering said solid polymeric material.
 7. The methodof claim 1, further comprising: (f) cooling said depolymerized polymericmaterial.
 8. The method of claim 7, further comprising: (g) purifyingsaid depolymerized polymeric material.
 9. The method of claim 8, whereinsaid purifying step employs one of flash separation, absorbent beds,clay polishing and film evaporators.
 10. The method of claim 1, whereinsaid depolymerized material is added to said pre-wax mixture via anin-line pump.
 11. The method of claim 1, wherein said pre-wax mixturecomprises said solid polymeric material and atactic polypropylene. 12.The method of claim 1, further comprising: (f) employing gas and oilproduced during purification of said depolymerized polymeric material asfuel for at least one step of said method.
 13. The method of claim 6,wherein said filtering step employs a screen changer.
 14. The method ofclaim 6, wherein said filtering step employs a filter bed.
 15. Themethod of claim 1, wherein said depolymerization process employs acatalyst.
 16. The method of claim 15, wherein said catalyst is supportedon zeolite or alumina.
 17. The method of claim 1, wherein saiddepolymerization process employs a second reactor.
 18. The method ofclaim 17, wherein said reactors are connected in series.
 19. The methodof claim 17, wherein said reactors are stacked vertically.
 20. Themethod of claim 1, wherein said reactor comprises a static mixer.